iTunes best audio chain?

I must confess that the migration to pure digital audio slightly does my head in as everybody seems to want to control/tweak the signal... :confused:



Here we go - at present I have the following chain:



iTunes (lossless files) -> Ethernet via power line -> Airport Express ->RCA split cable -> Preamp -> Amp -> speakers



So in the current setup, the D/A conversion takes place in the Airport Express.



I have now purchased an external DAC so logic would say to install it as above and to replace the RCA cable with an optical cable between the Airport Express and the DAC. I would also add BitPerfect to control iTunes for good measure. At some stage I might decide to get rid of the preamp altogether, but that's another story...



Here are my specific questions:



1) If I want to use higher sampling files (say 24bit/96kHz) , I know iTunes will accept them but Airport Express has a habit of downsampling files. Would using the AE without its DA action mitigate that? Does it become a passive box?



2) Is there a benefit of bypassing the AE altogether, for example by running a length of cable to use the USB of my DAC? In that case I am likely to need about 2 metres of cable: am I better with long USB/short audio cables or short USB/long audio?



3) More generally, has anybody come across a clear and up to date primer on digital audio: this is like learning a new language! :eek:



Thanks!

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